غازات الدم الشرياني

1. Arterial Blood Gas

2. Objectives
•State the normal ABG value ranges.
•Define acidosis and alkalosis according to ABG
values.
•Name the four categories of acid-base disorders.
•Understand how to use the ABG analyzer.

3. What is the purpose of measuring acid-base?
• Acid-base disorders are common in critically ill patients
and assessment of acid-base status may indicate specific
diagnoses or therapeutic interventions.
• The presence of a metabolic acidosis should suggest
hypoperfusion and prompt further assessment of
adequacy of oxygen balance.

4. What is an ABG?
•Measures level of acidity, level of O2 and CO2.
•Actual measurements are: pH, pO2 and pCO2.
•To check how well your lungs are able to move O2
and remove CO2 from blood.

5. ABG analysis
• Arterial blood gas analysis (ABG) should be available in
the ICU.
• In resource limited settings, ABG analysis may be
available or frequent measurements not possible.
• Consider use of end-tidal CO2 in conjunction with SpO2
and RR to make assessment, understanding the
limitations.

6. What does it measure?
•PaO2- partial pressure of O2 in blood (dissolved)
•PaCO2- partial pressure of CO2 in blood
•pH- hydrogen ions
•HCO3- buffer that keeps the pH from becoming too
acidic.
•SatO2- amount of O2 in blood

7. ABG analysis
 Benefits  Limits
• Measures pH, PaCO2, PaO2
• Informs about ventilation and acidosis
• May also be used to measure lactate,
haemoglobin, potassium
• Invasive arterial puncture
• Heparinized syringe
• Rapid transfer (on ice if > 20 minutes to lab)
• Blood gas analyser machine
• Carbon monoxide level not detected on all
machines.

8. Evaluation of Acid-Base Disorders
Analysis of acid-base disorders in seriously ill patients
requires a systematic approach. Several processes
possible:
• Metabolic acidosis
• Metabolic alkalosis
• Respiratory acidosis
• Respiratory alkalosis

9. Normal values
No. Characteristics Normal range
1 pH 7.35-7.45
2 PCO2 35-45 mm Hg
3 PO2 80-100 mm Hg
4 O2 sat 95-100%
5 HCO3 22-26 mEq/l
Note: PO2 is the amount of O2 dissolved in blood while O2 sat is the
hemoglobin with O2 attached to each and measured in %.

10. Conditions
No. Condition Metabolic Respiratory
1 Acidemia pH<7.35 PHCO3<22 PCO2>45
2 Alkalemia pH>7.45 PHCO3>26 PCO2>35

11. Key points
• The normal pH of blood is 7.35-7.45.
• If pH is < 7.35 its acidosis and if > 7.45 its alkalosis.
• The normal value of pCO2 is 35-45 mm hg and HCO3 is 22-
26 mEq/l.
• In respiratory disorders, the pH and pCO2 should be moving
in opposite directions while HCO3 remains WNL.
• In metabolic disorders, pH and HCO3 moves in the same
direction with pCO2 WNL.

12. Questions
•The normal pH range of blood is ______ to ______.
•Acidosis means pH is ______.
•Alkalosis means pH is ______.
•What four acid-base conditions are possible?
•pH =7.30, HCO3=20 mEq/l and CO2= 40mm Hg
• What is the condition?